Potable (drinking) water is commonly found in large commercial transport vehicles such as aircraft, railroad passenger cars, buses, boats and ships. Such water is placed on board these transport vehicles for use as drinking water, making ice cubes, culinary, cleaning, and other sanitary purposes. Care must be taken to assure that harmful bacteria and organisms are not present and/or multiplying in the water found inside the potable water storage and distribution systems in these conveyances. Some organisms can live and multiply very rapidly under certain conditions. Most frequently cited to be of concern are coliform, ecoli, and legionella, but other common bacteria in domestic water supplies in the United States, Canada, and other countries include, but are not limited to, salmonella typhia, shingella sonnei, dysenteria, flexneri, boydii, vibro cholerae, campylobacter jejuni, yersinia enterocolitica, plesiomonas shigellojodes, and aeromonas hydrophila. Therefore, care is needed in the treatment and handling of water intended for such uses.
Within the United States, the Environmental Protection Agency has a responsibility for regulatory enforcement of the Safe Water Drinking Act of 1974. The Act covers, among other things, municipal drinking water supplies and other water supplies being used by the public. Other politically stable and economically developed countries have similar agencies with similar responsibilities. It is recognized by these agencies that it is economically impossible to provide absolutely pure water. There are, however, achievable, appropriate, and economical limits to the concentration of chemical, mineral, and organic contaminants. These contaminant concentrations are very low and generally do not represent a health threat to the general population.
Most of the watering points used to transfer water into the transport are filled using municipal, and otherwise regulated, treated water supplies. Acceptably low concentrations of some offensive organisms are routinely introduced into watering points and consequently could find their way into the transport's potable water storage tank(s). Given the right conditions, these offensive organisms can grow and multiply and develop higher concentrations that can be harmful to otherwise strong and healthy people. These organisms can also form biofilms within watering points and a transport's potable water storage tank(s). Such biofilms can re-contaminate watering points and the transport's potable water storage tank(s) even after they have been emptied, flushed, and refilled.
One method for filling a storage tank(s) in a transport's potable water system is the utilization of a potable water station which may take the form of a potable water cabinet (PWC). The PWC is essentially a cabinet containing piping, hose, hose reels, and other apparatuses compatible with drinking water that are used to convey water from the municipal water supply into the transport's potable water storage tank(s).
There are (2) conditions that foster the rapid growth (higher concentrations) of organisms and biofilms in the water within these PWC's. These are temperature and stagnation.
Temperature: Studies have shown that, generally, the optimum temperature under which various harmful bacteria and organisms multiply is 98.6 degrees Fahrenheit. However, bacteria can proliferate at temperatures between 59 degrees Fahrenheit and 149 degrees Fahrenheit. Bacteria will generally die at temperatures above 149 degrees Fahrenheit.
Stagnation: Water that is not flowing provides a quiet environment where bacteria can grow and form biofilms. While good operating practices require the regular flushing of potable water cabinets to mitigate the growth of bacteria in otherwise stagnant water, there is no assurance that operators always flush PWC's in a proper and consistent fashion.